Diameter Maintenance and J. Bournelle (Ed.)
Extensions (DIME) GET/INT
Internet-Draft G. Giaretta
Expires: December 21, 2006 Telecom Italia
H. Tschofenig
Siemens
June 19, 2006
Mobile IPv6 Bootstrapping using Diameter in the Split Scenariodraft-ietf-dime-mip6-split-00
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Copyright (C) The Internet Society (2006).
Abstract
In Mobile IPv6 deployment a need for an interaction between the Home
Agent, the AAA infrastructure of the Mobile Service Provider (MSP)
and the Mobility Service Authorizer (MSA) has been identified. This
document describes how Diameter can be used to perform AAA
functionalities for the Mobile IPv6 service in the "split" scenario.
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Internet-Draft MIP6 Bootstrapping with Diameter June 20061. Introduction
In Mobile IPv6 deployment, authentication, authorization and
accounting issues in the protocol operations are approached by using
the AAA infrastructure. [9] presents a number of bootstrapping
scenarios using the HA-AAA interface and defines a list of
requirements that have to be fulfilled. This document deals with the
functional capabilities of the Diameter protocol as a AAA protocol
applicable for the split scenario.
This document focuses only on the split scenario. A separate
document [10] describes a Diameter application for bootstrapping
MIPv6 for the integrated scenario.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [1].
The MIPv6 bootstrapping terminology is taken from [2].
3. Bootstrapping Mobile IPv6 in the Split Scenario
In the split scenario for bootstrapping Mobile IPv6 [3], the Mobile
Node (MN) discovers a Home Agent (belonging to the Mobility Service
Provider (MSP)) through DNS. Then, the Mobile Node uses IKEv2 [4] to
setup IPsec SAs. Use of IKEv2 also provides a way to authenticate
the MN by the Mobility Service Authorizer (MSA). Note that in the
same time, the Mobile Node can authenticate the Home Agent. IKEv2
supports the Extensible Authentication Protocol (EAP) to run an EAP
method between the MN and the EAP server that is often separated from
the IKEv2 responder, i.e., the HA in our scenario. As such, the MN
can reuse its credentials (obtained from the MSA) to be authenticated
for the IPv6 mobility service. As outlined in [4] a HA-AAA interface
is needed. Since, EAP is used to authenticate the MN, the interface
between the Home Agent and the AAA server will be based on the
Diameter EAP application [5]. Figure 1 represents the architecture
of the split scenario.
+-------+ IKEv2 +----------------+ Diameter EAP +----+
| Mobile| | Home Agent/ | | |
| Node |<----------->| Diameter Client|<-------------------->|AAAH|
+-------+ +----------------+ +----+
Figure 1: Diameter EAP for HA-AAA in the Split Scenario
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Figure 2: IKEv2 Diameter EAP Message Flow
The interaction between the MN and the HA starts with an IKE_SA_INIT
to setup the IKE SA. The MN indicates its desire to use EAP by not
including the AUTH payload in the third message. The MN indicates
its identity (e.g Network Access Identitifer) using the IDi field.
If the Home Agent, acting as an IKEv2 Responder, supports EAP for
authentication and relies on a remote AAA server, the Diameter client
part of the Home Agent sends a Diameter-EAP-Request (DER) message
containing the identity in the EAP-Payload AVP and in the User-Name
AVP. The AAAH chooses an authentication method and sends the first
EAP-Request in the Diameter-EAP-Answer message. During the EAP
authentication phase, the HA relays EAP packets between the MN (EAP
client) and the AAAH (Home EAP server). If the authentication
succeeds and if the MN is authorized to use Mobile IPv6 service, the
AAAH sends a DEA message containing the EAP-success and the AAA-Key
derived from the Master Session Key (MSK) exported by the EAP method.
Some specific configuration elements may also be sent in AVPs. Note
that EAP methods that do not derive keys are not recommended since
they cannot bind the EAP method authentication to the IKEv2
authentication. In the latter message, the MN and the HA finalize
the IPsec SAs setup to protect Mobile IPv6 signalling.
4. Use of Diameter EAP for the Mobile IPv6 Split Scenario
In the split scenario, the Home Agent uses the AAA infrastructure in
order to perform authentication, authorization and accounting for the
Mobile IPv6 service. This document proposes to reuse the Diameter
EAP application [5] since EAP is used by the HA to authenticate the
MN inside IKEv2.
However, the Diameter EAP application has been designed to perform
AAA for the network access service. As the Mobile IPv6 service is
different from the network access service, it appears that a Diameter
server needs a way to make this distinction. Indeed, even if the
authentication is provided by the EAP method, authorization and
accounting for network access and IPv6 mobility might be different.
The AAA server needs to explicitly authorize the Mobile IPv6 service.
It may also need to configure specific parameters for the Mobile IPv6
service such as the type of Home Address to provide to the MN.
Accounting may also require other parameters than those defined for
network access.
[Editor's Note: It is not clear at this point of time which approach
is the best to handle this. For this reason, this document explains
two possible approaches.]
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Internet-Draft MIP6 Bootstrapping with Diameter June 20064.1. NAS-Port-Type AVP
As explained below, the AAA server needs a way to identify that it is
performing AAA operations for the Mobile IPv6 service. One way to do
this is to require that the Home Agent puts the NAS-Port-Type AVP
indicating that it is a Mobile IPv6 Home Agent in the first DER
message. This would be formulated as: "The Home Agent MUST include
the NAS-Port-Type AVP". This requires a change in the current ABNF
definition of this message. The AAA server would have to check the
presence of this AVP in the first received DER message and would have
to recognize the new type defined for the Home Agent.
[Editor's Note: It is not clear at this point of time if this change
in the ABNF definition would require a new Application-Id.]
Moreover, the NAS-Port-Type AVP is defined as: "The NAS-Port-Type AVP
(AVP Code 61) is of type Enumerated and contains the type of the port
on which the NAS is authenticating the user. This AVP SHOULD be
present if the NAS uses the same NAS-Port number ranges for different
service types concurrently" (see [6]). Hence, if the DIME WG decides
to use this approach, it is necessary to define a new type for Home-
Agent.
If an operator wants to use one AAA server for network access and
another one for IPv6 mobility service then the some messages may be
routed to the wrong AAA server since routing is also based on the
Application-ID.
4.2. A new Application ID
The second approach is to require a new application ID for the Mobile
IPv6 service. In this case, all messages will be correctly routed to
the right Diameter Application. This specific application will
specifically handle all AAA Operations for the Mobile IPv6 service as
it is done for Mobile IPv4 (cf. [7]). However, the protocol
description requires that the new application needs to copy the
Diameter messages from the Diameter EAP application.
The problem with defining a new Application ID is that every proxies
on the path would need a new code to understand this application.
4.3. Accounting for the Mobile IPv6 Service
Concerning Accounting, the Diameter Mobile IPv4 Application [7]
defines the following AVPs: Accounting-Input-Octets (Number of octets
in IP packets received from the user), Accounting-Output-Octets
(Number of octets in IP packets sent by the user, Accounting-Input-
Packets (Number of IP packets received from the user), Accounting-
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Internet-Draft MIP6 Bootstrapping with Diameter June 2006
Output-Packets (Number of IP packets sent by the user).
These AVPs may be re-used for the Mobile IPv6 service. However, due
to some optimizations for Mobile IPv6, the HA may not see all the IP
traffic resulting from the activation of this service.
[Editor's Note: As the document describing goals for this interface
is not finalized, other parameters may be needed in the future.]
5. Goals
In this section, we present how the goals for a HA-AAA interface
presented in [9] are met by this proposal. Note that the two
approaches presented above does not affect what is described here.
[Editor's Note: the goals presented here are those described in [9].
Future revision of the mentionned document will affect this section.]
5.1. General goals5.1.1. G1.1 - G1.4 Security
As design goals for an AAA interface, G1.1 - G1.4 goals specify
standard requirements for a AAA protocol - mutual authentication of
the peers, integrity, replay protection and confidentiality. The
Diameter Base Protocol requires IPsec or TLS to provide hop-by-hop
security.
5.1.2. Dead peer detection - the HA-AAA interface SHOULD support inactive peer detection.
Two possible approaches might be considered here:
o The AAAH server and the Home Agent establish a transport
connection between each other. It is the case if the Diameter
Client of the HA has a direct route to its AAA server. In this
case Diameter heartbeat messages called Device-Watchdog-Request/
Answer [8], which are exchanged over this connection to test for
its aliveness, can be used to detect inactivity between the two
Diameter peers.
o The AAAH server and the Home Agent do not have transport
connection. In this case inactive peer detection functionality
should be provided into the Diameter session - service stateless
Diameter sessions might be established between the AAAH server and
the range of MSP's Home Agents for detecting HAs availability.
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Internet-Draft MIP6 Bootstrapping with Diameter June 20065.2. Service Authorization5.2.1. G2.1. The HA-AAA interface SHOULD allow the use of Network Access Identifier (NAI) to identify the mobile node.
Identification by the User-Name AVP [8], which has a format
consistent with the NAI specifications, is common for Diameter
applications. Diameter provides functionality for routing of
Diameter requests based on the information included in the User-Name
AVP.
The Mobile Node provides its NAI using the IDi field during the IKEv2
exchange with the HA.
5.2.2. G2.2. The HA SHOULD be able to query the AAAH server to verify Mobile IPv6 service authorization for the mobile node.
The goal of this document is to explain how to use Diameter to
perform AAA operations for the Mobile IPv6 service. The
Authentication is done through the use of EAP. The Mobile IPv6
service Authorization is an explicit goal of this document.
[Editor's note: As explained above, how the AAA server know that it
is for Mobile IPv6 service has not yet been decided by the DIME WG.]
5.2.3. G2.3. The AAAH server SHOULD be able to enforce explicit operational limitations and authorization restrictions on the
HA.( e.g. packet filters, QoS parameters).
Several present Diameter applications, standardized or under work-in-
progress address an operation and authorization control for specific
services and have defined appropriate AVPs. The NAS-Filter-Rule AVP,
defined by Diameter NASREQ application [6], provides IP packet filter
description. QoS-Filter-Rule AVP defined by Diameter NASREQ
application and by the Diameter QoS application [11] provide QoS
parameter description. The Credit Control application [12] provides
support for prepaid services, tariff switching, cost control over
requested services. The available funcationalities might be re-used
in this document.
5.2.4. G2.4 - G2.6. Issues addressing the maintenance of a Mobile IPv6 session by the AAAH server, e.g. authorization lifetime,
extension of the authorization lifetime and explicit session
termination by the AAAH server side.
Diameter base protocol provides a powerful set of commands and AVPs
for management of the authorization and accounting sessions. A
number of AVPs (Auth-Lifetime-AVP, Grace-Period-AVP, Session-Timeout-
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Internet-Draft MIP6 Bootstrapping with Diameter June 2006
AVP) handle the duration (in time) of an authorization session [8].
Additional AVPs for measuring the authorization duration in units
different that time are specified too [12]. Exchanging of
application specific authorization request/answer messages provides
extension of the authorization session. Initiation of the re-
authorization by both sides could be supported. Both sides could
initiate session termination, by using Diameter Session Termination
and Abort Session messages.
All these are applied to the Diameter session used for authorization
of a Mobile IPv6 session and need to be applied appropriately to this
Mobile IPv6 session too.
5.3. Accounting - G3.1. The HA-AAA interface MUST support the transfer of accounting records needed for service control and charging
Diameter accounting protocol provides a variety of options - real-
time accounting, event/session-type accounting records, fault
resilience, correlation of accounting records. Requirements for the
accounting services over AAAH-HA interface are standard. Definition
or re-used of AVPs for the specific accounting records combined with
the functionality of the Diameter accounting protocol should provide
desired accounting services.
5.4. Mobile Node Authentication (G4.1.)
These issues require the functionality of AAAH server working as a
back-end authentication server and HA working as NAS and EAP
authenticator in pass-through mode for providing a mobile node
authentication. This functionality is provided by the Diameter
NASREQ [6] and the Diameter EAP applications [5] application, and
will be re-used in this document.
6. Security Considerations
[Editor's Note: Since the document is not complete it is necessary to
state that the security consideration section is incomplete as well.
Hence, it is only possible to refer to the security issues raised in
the Mobile IPv6 and Diameter protocol related documents mentioned
here, such as [9] and [8].]
7. IANA Considerations
[Editor's note: Since the document is not complete, the IANA
considerations is incomplete as well.]
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